Investigating circulating miRNAs as predictors of therapeutic response in metastatic castration-resistant prostate cancer

Metastatic castration-resistant prostate cancer (mCRPC) is advanced prostate cancer (PCa) that has developed resistance to first-line androgen deprivation therapies. For mCRPC, several treatments are available, but the response rate is usually low (<50%) for any treatment. Therefore, a biomarker that can predict response to a particular treatment will be beneficial as predicted non-responders could be offered alternative treatments that may be more effective and avoid unnecessary side effects. microRNAs (miRs) are a class of short non-coding RNA and circulating miRs (c-miRs) refer to extracellular miRs found in the blood. c-miRs hold many characteristics of an ideal biomarker, such as high stability, and have been investigated as biomarkers in various diseases including PCa. We hypothesised that pre-treatment levels of specific c-miRs in mCRPC patients can predict their response to Cabazitaxel (CBZ), which is a taxane chemotherapy used in treatment for mCRPC. PROSELICA is a clinical trial, in which mCRPC patients were treated with CBZ as second-line chemotherapy. Using pre-treatment plasma from PROSELICA, the levels of 41 potentially CBZ response associated c-miRs were measured in 21 responders and 21 non- responders with a Fireplex assay. Compared to responders, non-responders had significantly higher pre-treatment levels of 8 c-miRs, including miR-132-3p. This up-regulation of c-miRs could be technically validated using modified qPCR. Individually, these 8 up-regulated c- miRs had CBZ response predictive power with AUROC around or greater than 0.7 and 7 of them were also shown to be prognostic of overall survival in CBZ-treated mCRPC patients. Next, we decided to validate the findings in separate 108 patients from PROSELICA. Although the predictive power of these c-miRs were not confirmed, up-regulation of miR- 132-3p in non-responders and the prognostic power of 7 c-miRs were validated. Lastly, the potential sources of these 8 c-miRs were explored. Using publicly available datasets, the expression of these 8 c-miRs were confirmed in CRPC tissues. Subsequently, the release of these c-miRs from tumours was observed in vitro using Explanted tissues from prostate biopsies. In conclusion, specific c-miRs are prognostic and potentially predictive of CBZ response in mCRPC patients and these prognostic/predictive c-miRs may come from tumours, suggesting they may play a role in CBZ-response in tumours.Open Acces

A novel role for GSK3β as a modulator of Drosha microprocessor activity and MicroRNA biogenesis

Regulation of microRNA (miR) biogenesis is complex and stringently controlled. Here, we identify the kinase GSK3β as an important modulator of miR biogenesis at Microprocessor level. Repression of GSK3β activity reduces Drosha activity toward pri-miRs, leading to accumulation of unprocessed pri-miRs and reduction of pre-miRs and mature miRs without altering levels or cellular localisation of miR biogenesis proteins. Conversely, GSK3β activation increases Drosha activity and mature miR accumulation. GSK3β achieves this through promoting Drosha:cofactor and Drosha:pri-miR interactions: it binds to DGCR8 and p72 in the Microprocessor, an effect dependent upon presence of RNA. Indeed, GSK3β itself can immunoprecipitate pri-miRs, suggesting possible RNA-binding capacity. Kinase assays identify the mechanism for GSK3β-enhanced Drosha activity, which requires GSK3β nuclear localisation, as phosphorylation of Drosha at S300 and/or S302; confirmed by enhanced Drosha activity and association with cofactors, and increased abundance of mature miRs in the presence of phospho-mimic Drosha. Functional implications of GSK3β-enhanced miR biogenesis are illustrated by increased levels of GSK3β-upregulated miR targets following GSK3β inhibition. These data, the first to link GSK3β with the miR cascade in humans, highlight a novel pro-biogenesis role for GSK3β in increasing miR biogenesis as a component of the Microprocessor complex with wide-ranging functional consequences

Single-molecule amplification-free multiplexed detection of circulating microRNA cancer biomarkers from serum

miRNA profiling from patient blood can be used for cancer diagnosis. Here the authors present an electro-optical nanopore sensing platform which allows sensitive and specific miRNA detection directly in human serum and apply to monitoring of miR-141-3p and miR-375-3p in different stage of prostate cancer